Telephone-exchange system.



G. DEAKIN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR.8|1912.

1,142,678. Patented June 8, 1915.

WITATESSES.

UNITE 63323.15 OF BERKELEY, CALIFORNIA.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters IPatent.

Patented June 8, 1915.

Application-filed March a, 1912. Serial n. 682,390.

To all whom it may concern: 7

Be it known that I, GERALD Dmnm, a citizen of the United States,residing at Berkeley, in the county of Alameda and State of California,have invented certain new and useful Improvements in Telephone- ExchangeSystems, of which the following is a specification.

My invention pertains to an improved automatic repeater circuit adaptedto receive electric impulses from a telephone station equipped with anautomatic calling device, and to transmit in modified form, the electricimpulses so received and in such a manner as to operate switches in anautomatic telephone central oflice, which may be of the type whichcannot be operated in direct connection with the subscribers stationcalling device.

At the present time, there are in Wide commercial use, two types ofautomatic telephone exchange systems, mechanically similar butelectrically dissimilar. In the first and older type, the impulsesoriginated at the calling telephone station for the operation of theswitches at the central oflice, are sent alternately over the two lineWires, the earth forming the return path in each case. After the calledline'has been selected in the central oliice, by the proper switch, thecall bell at the called station is caused to ring by depressing aringing key at the calling station, Which grounds one side of thecalling line. The release of a completed connection thus established, iseffected by simultaneously grounding both sides of the calling line. Inthe second and later system, the connection is established by rapidlymale in In this system the earth is not used in establishing aconnection. The release of a completed connection thus established, isefiected by permanently opening the calling line circuit. The callingdevice required for use in connection with the later system is a verysimple piece of mechanism, consisting merely of two contact springs,adapted to alternately break and make contact when the device isoperated. In the older system, the calling device is much morecomplicated, in that it has to apply a series of grounds to one side ofthe line and then a ground to the other each time it is operated.Furthermore, the hookswitch has to be connected with the calling devicemechanism or otherwise adapted to momentarily ground both and breakingthe calling line circuit.

sides of the line, when the'receiver is replaced upon it.

The object of my improved repeater cir-. cult is to permit the use ofthe simple make and break calling device at the subscribers station, inconnection with the older type of central oflice equipment, requiringthe use of an earth return circuit for its operation. Typical selectorand connector switches of the ,old type, are described in United andbreak calling device at the subscriber's station and automatic switchesat the central oflice, requiring the use of both sides of a pair ,ofline wires with an earth return for the establishment of a connection,and the simultaneous grounding 01 both sides of the line for releasingthe connection.

In the repeater circuits now in common use the talking circuit isnormally closed through the repeater. Should this talking circuitcontain condensers or other form of electrical capacity, the electricimpulses received and transmitted will be interfered with by thecharging and discharging of the condensers. To overcome this point thetalking circuit in my improved-repeater is adapted to remain open untilthe ringing key at the'calling station is depressed. The accompanyingdrawing illustrates my improved repeater circuit associated with asubscribers station telephone circuit, at A, equipped with a simple makeand break calling device. At B are shown the controlling line relays ofan automatic central oflice switch of the ground return type.

At A is shown a simple form of subscribers station telephone circuit,consisting of a transmitter, receiver, switchhook, ringing key R, and at3, contact springs of the calling device, adapted to rapidly open andclose the line circuit, when the device is op.- erated.

L and L represent two line wires connecting station A with the repeater.

C and D represent relays of the type ordinarily used in telephonecircuits. E, F, .G

and H represent similar relays, the magnetic cores of which are providedwith copper sleeves or shortcircuited windings, or otherwise adapted tomake the relays sluggish in resuming their normal position when onceenergized.

L and M represent condensers.

L and L represent two conductors or members of the trunk circuit,connecting the repeater with the central olfice switches, which switchesare adapted to automatically extend and complete the connection.

J and K represent line relays controlling the operation of an automat1cswitch. lit should be understood that relays J and K representcorresponding relays associated with different switches involved inestablishing a connection.

A source of current supply, preferably a storage battery, is shown at 2and at 1 an earth connection.

An examination of the patents previously referred to will show that theautomatic switches of the general type covered by them, are adapted toselect, but not engage in electrical contact, the trunk or lineterminals, corresponding to the digit called by the calling station,when the corresponding number of successive grounds are placed upon oneof the wires of the line circuit. This wire is usually known as thevertical side of the line. The switches are caused to engage inelectrical contact the trunk or line terminal selected, when a ground isplaced upon the opposite or remaining line wire. This wire is usuallycalled the rotary side of the line. In the accompanying drawing. theconductor L may be considered the vertical side of the line andconductor L the rotary side of the line. Relay J in each switch involvedin a connection, will then control the selective powers of the switchand relay K the power of the switch to engage in electrical contact thetrunk or line terminal selected by relay J. After the called lineterminals have been picked up the call bell at the called station iscaused to ring when the vertical side of the line is grounded. A furtherexamination of the patents will show that the release of an establishedconnection is accomplished by simultaneously grounding both sides of thecalling line. It will therefore be seen that my improved repeatercircuit must be capable of supplying to the vertical wire of the line, aseries of grounds corresponding to the digit called by the callingstation and at the end of each such series must also be capable ofsupplying a ground to the rotary side of the line. After the selectionof the called line terminal, the repeater must be capable of groundingthe vertical wireof the line whenever the ringing key at the callingstation is depressed. At the end of conversation when the receiver isreplaced greases upon the hookswitch at the calling station, therepeater must be capable of simultaneously grounding both sides of theline for a moment. In nearly all of the recent automatic telephoneinstallations, a small switch known as a line switch has been installed.The function of this switch is to connect the calling subscriber with anidle selector, thereby reducing the number of selectors required sinceit is safe to assume but a small portion of the lines will be used atany one time. In one type of central oflice equipment now widely used,the line switch is caused to connect the calling line with an idleselector by means of a preliminary ground momentarily placed upon therotary side of the calling line, just prior to the sending of the firstseries of impulses over the vertical side of the line. In my improvedrepeater circuit, this is accomplished by momentarily grounding therotary side of the line immediately following the removal of thereceiver from the hookswitch. As before indicated, the call receivingbranch of my repeater circuit is adapted to receive calls from a callingstation equipped with a calling device, consist ing of a pair of contactsprings, adapted to rapidly open and close the line circuit as manytimes as indicated by the digit called. For example, when the digiteight is called, the line circuit is rapidly opened and closed eighttimes.

From the preceding paragraph it may be said that that function of myimproved repeater is to receive impulses from a calling telephonestation equipped with a calling device adapted to make and break ametallic line circuit and then to transmit the impulses thus received tothe central oflice apparatus, first by grounding one side of the lineherein called the vertical side of the line, as many times as the linecircuit is broken at the calling station, depending upon the digitcalled, and then momentarily grounding the other side of the line hereincalled the rotary side of the line. Upon completion of the calling ofthe desired numher, the repeater must be capable of grounding thevertical wire each time the ringing key is depressed at the callingstation. Upon the permanent opening of the calling line circuit, whichtakes place when the receiver is replaced upon the hookswitch, therepeater momentarilyigrounds both sides of the line toward the centraloliice, thereby releasing the connection.

The operation of my improved repeater circuit is as follows: When thereceiver is removed from the hookswitch at station A, the line circuitis closed, current flowing from 1, through one winding of relay D, onewinding of relay C, L calling device contacts 3, transmitter, hookswitchcontacts, primary winding of induction coil, I), re-

' cial purpose.

maining windin' of relay C, remaining winding of relay battery 2, to theearth 1. The current thus caused to flow energizes relay C. Relay Dremains inert, its winding being differentially connected for this spe-The operation of relay C opens contact between 7 and 8, 5 and 6, andcauses contact to be made between 5 and 4, thus energizing relay F andmomentarily relay H through contacts 23 and 24. Relay F closes contactbetween 20 and 21, 26 and 25 and breaks contact between 21 and 22 and 24and 23. The momentary operation of re-- lay H grounds conductor L", from1, through 29, 30, 32, 31 to L. The object of this preliminary ground isto trip the line switch if one is used, as previously described. Whenrelay H resumes its normal position, the earth connection is removedfrom conductor L by the opening of contact between,

31 and 32. The repeater is now ina position to receive and transmitimpulses from the calling station. As before stated, the impulsesreceived from the calling station consist of a series of interruptionsof the calling line circuit and are produced by operating the callingdevice. The number of times the line circuit is opened and closedcorresponds to the digit called. The speed of these interruptions is soadjusted as to permit relay C to follow them, but not the sluggishrelays F. In this way, the repeater is held in its operative conditionduring calling. Assume now that station A calls the first digit of thedesired number. Relay C resumes its normal position as many times as theline circuit is broken between the calling device contacts 3. Each timerelay C resumes its normal position, it closes contact between 5 and 6and between 7 and 8 and breaks contact between 4 and 5. The closing ofcontact between 7 and 8 operates sluggish relays G and H, a circuitbeing closed from 1 through 7, 8, 26,25, windings of G and H, 2 to 1.Relays G and H being sluggish, do not chatter when relay C operates inresponse to the impulses received from the calling device 3. The closingof contact between 5 and 6 causes a ground to be placed upon conductor Lthereby causing current to flow from 1, through 5, 6, 21, 20, 12 and 13,conductor L winding of J, 2 to 1. As before stated,-relay J controls theselective powers of the automatic switch. The result.

is that the switch is caused to proceed in the selection of the numbercalled, each time a ground is placed upon the conductor L After thecalling device at station A has completed an operation, that is, afterit has sent a series of impulses in response to the digit called, theline circuit through the calling station, A, is again permanently closedthrough contacts 3. The result is that relay C remains energized. Thepermanent open- -$5 ing of contact between 7 and 8 allows relays thevarious relays.

G and H to resume their normal position.

The adjustment of relay G is made such that it resumes itsnormal'position before relay H. Therefore, there is an interval duringwhich a ground is placed 'on conductor L, from 1, through 29, 30, 32, 31to L. Relay 'K is thus energized. As before stated, this relays in theselectors and in the connector. I

After the final digit has been called, ringing key R at stationA isdepressed, thereby grounding both sides of the calling line. The resultis that the differential relay D is unbalanced by the short circuitingof its earthed winding. The unbalancing of the relay causes it tooperate, and in so doing breaks contact between 9 and 10 and closescontact between 10 and 11. This results in the operation of relay E,which relay remains locked up during the remainder of the connection andgrounds conductor L from 1, through 29, 30, 32, 35, 11, 10, 14, 13 toLi. The operation of relay E is caused by the closing of a circuit from1 through 10, 17, 16, winding'of E, 2 to 1. The energizing of relay Eopens circuit between contacts l6 and 17 and closes the locking circuitfrom 1, through 5, 4, 15, 16, .winding of E, 2 to 1. The operation ofthis relay also connects the calling line branch of the repeater to thecalled line branch of the repeater. This is effected by the making ofcontact between 13 and 14 and between 18 and 19.

When ringing key R is allowed to assume its normal position, relay D isdenergized, thereby removing the ground connection from conductor Lrelay E, as before stated, remains energized until released at the endof the connection. Each time the ringing key R is depressed, a ground issimilarly applied to conductor L thus operating line relay J of theconnector involved in establishing the connection, thereby energizingthe ringing relay of the connector and causing the call bell at thedistant station to ring. When the called station answers, conversationmay be carried on. The function of condensers L and M is to transmit thehigh frequency voice currents but not the direct current acquired forthe operation of At the end of conversation, the receiver at the callingstation is replaced upon the hookswitch, thus permanently opening thecalling line circuit. Relay C now resumes its normal position, breakingcontact bet-ween 5 and 4 and making contact between 5 and' 6 and 7 and8. This opens the circuit through both relays E and F, allowing them toresume their normal position. Prior to the deenergizing of relay F, acircuit is momentarily established from 1, through 7, 8, 26 and 25,winding of G, Winding of H, 2 to 1. Relays G and H now operate andremain energized until con tact is opened between 25 and 26, whereuponboth relays resume their normal position. As before stated, however,relay G resumes its normal position first. Therefore, during theinterval between the falling back of relay G and relay H, a ground isplaced on both sides of the line toward the central otiice, in one casefrom 1, through 29, 30, 32, 31 to If and in the other case from 1,through 5, 6, 21, 22, 28, 27. 34, 33 to L The result of thissimultaneous grounding is that relays J and K are simultaneouslyenergized, and as before stated, this simultaneous action results in thedisconnection of the automatic central oiiice apparatus. When relay Hfinally resumes its normal position, the ground is removed from bothconductors L and L and the circuit of the repeater resumes its normalposition.

One of the principal advantages of the repeater circuit just described,lies in the fact that the line conductors L and L in the calling linebranch, and the line conductors L and L in the called line branch arenot engaged in electrical connection during calling. Experience hasshown that Where this is not the case, the charging and discharging ofcondensers L and M which occurs when the calling line circuit is madeand broken, seriously interfered with the transmission of sharp andclear impulses to the central office apparatus.

Having thus described the invention, what is claimed as new is:

1. In a telephone exchange system, a line circuit, a repeater circuit,means for operating the repeater circuit. a trunk circuit terminating inan automatic switch for connecting to a called substation, condensers,and means for connecting the line and trunk circuits through thecondensers to establish a talking circuit after the completion of theconnection with the called substation.

2. In a telephone exchange system, a line circuit, a repeater circuit.means for operating the repeater circuit, a trunk circuit terminating inan automatic switch. condensers, and means operated upon the groundingof one side of the line at the subscribers station for connecting theline and trunk circuits through the condensers to establish a talkingcircuit, the last means being operable by the operating means of therepeater circuit.

3. In a telephone exchange system, a line circuit, a repeater circuit, atrunk circuitterminating in an automatic switch, means .responsive to aground impulses over meaeve for operating the repeater circuitcomprising a calling device and ringing device, con densers, and meansoperable by the ringing device aforesaid to connect the line and trunkcircuits through the condensers to establish the talking circuit.

4.. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device, anda relay adapted to be energized by the ringing device to connect theline and trunk circuits to establish a talking circuit.

5. In a telephone exchange system, a line circuit, a repeater circuit, atrunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,condensers, and a relay adapted to be energized by the ringing device toconnect the line and trunk circuits through the condensers to establisha talking circuit.

6. In a telephone exchange system, a line circuit, a repeater circuit, atrunk circuit terminating in an automatic switch, means for operatingthe repeater circuit compris ing a calling device and ringing device,and means operable by the ringing device aforesaid to connect the lineand trunk circuits to establish the talking circuit.

7. In a telephone exchange system, line and repeater circuits, a trunkcircuit terminating in an automatic switch, a calling device to operatethe repeater circuit, and means comprising a ringing device to groundthe line circuit and thereby connect the line and trunk circuits toestablish a talking circuit.

8. In a telephone exchange system, line and repeater circuits, a trunkcircuit terminating in an automatic switch, a calling device to operatethe repeater circuit, and means comprising a ringing device to groundthe line circuit to simultaneously ring the called subscriber andconnect the line and trunk circuits to establish a talking circuit, andsubscribers lines connected with the automatic switch.

9. In a telephone exchange system, the combination of line and repeatercircuits, a trunk circuit leading to an automatic switch, and saidrepeater circuit including means responsive to initial closure andsubsequent prolonged closure of the line circuit to ground one member ofthe trunk circuit, and

prolonged interruption of the line circuit, to ground both members ofthe trunk circuit.

10. In a telephone exchange system, the combination of a line circuit,means for clos ing the line circuit. means for momentarily interruptingsaid circuit, a repeater circuit, a trunk eircui, an automatic switchconnected to said trunk circuit and operable by the trunk circuit,

means in the repeater circuit responsive to said interruptions of theline circuit for grounding one member of the trunkcircuit, and meanscoiiperating with the means just mentioned on an initial closure of theline circuit for momentarily grounding-the other member of the trunkcircuit. A 11. In a telephone exchange system, the combination of a linecircuit, means for closing the line circuit, means for momentarilyinterrupting said circuit, a repeater circuit, a trunk circuit, anautomatic switch connected to said trunk. circuit, and operable byground impulses over the trunk circuit, means in the repeater circuitresponsive'to said interruptions of the line circuit for grounding onemember of the trunk circuit, means cooperating with the means justmentioned on an initial closure of the line circuit for momentarilygrounding the other member of the trunk circuit, and means responsive tosubsequent prolonged closure of the line circuit for grounding the lastmentioned member of the trunk circuit.

12. In a telephone exchange system, the combination of a line circuit,means for closing the line circuit, means for momentarily interruptingsaid circuit, a repeater circuit, a trunk circuit, an automatic switchconnected to said trunk circuit and operable by ground impulses over thetrunk circuit, means in the repeater circuit responsive to the initialclosure of the line circuit to ground one member of the trunk circuit,means in the repeater circuit responsive to said interruptions of theline circuit for grounding one member of the trunk circuit, and meansresponsive to subsequent prolonged closure of the line circuit forgrounding the other member of the trunk circuit.

13. In a telephone exchange system, the combination of a line circuit,means for closing the line circuit, means for momentarily interruptingsaid circuit, a repeater circuit, a trunk circuit, an automatic switchconnected to said trunk circuit, and operable by ound impulses over thetrunk circuit, means in the repeater circuit responsive to initialclosure of the line circuit to ground one member of the trunk circuitand responsive to prolonged interruption of the line circuit to groundboth members of the trunk circuit, means in the repeater circuitresponsive to said interruptions of the line circuit for grounding onemember of the trunk circuit, and means responsive to subsequentprolonged closure of the line circuit for ounding the other member ofthe trunk clrcuit.

14. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device, anddifferentially and inductively wound relays connected in series andbridged across the line circuit, so that the latter relay is responsiveto a closure of said line circuit, and the first-mentioned relayresponsive to agrounding of the said circuit by the ringing device.

15. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,differentially and inductively wound relays connected in series andbridged across the line circuit, so that the latter relay is responsiveto a closure of said line circuit, and the first-mentioned relayresponsive to a grounding of the said circuit by the ringing device, anda relay adapted to be energized by the ringing device to connect theline and trunk circuits to establish a talking circuit.

16. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,condensers, differentially and inductively wound relays connected inseries and bridged across the line circuit so that the latter relay isresponsive to a closure of said line circuit and the first-mentionedrelay responsive to a grounding of said circuit by the ringing device,and a relay adapted to be energized by the ringing device to connect theline and trunk circuits through the condensers to establish a talkingcircuit.

17. In a telephone exchange system a line circuit, a repeater circuit, atrunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,condensers, diflerentially and inductively wound relays connected inseries and bridged across the line circuit so that the latter relay isresponsive to a closure of said line circuit and the first-mentionedrelay responsive to a grounding of said circuit by the ringing device,and a relay adapted to be energized by the ringing device through theintermediation of the differential relay to connect the line and trunkcircuits through the condensers to establish a talking circuit.

18. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device, anda differentially wound relay bridged across the line circuit, notresponsive to closures of the line circuit, but responsive to agrounding of said circuit, whereby one side of the trunk circuit isgrounded.

19. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,

condensers, a differentially wound relay bridged across the linecircuit, not responsive to closures of the line circuit, but responsiveto a grounding of said circuit, whereby one side of the trunk circuit isgrounded, and a relay adapted to be energized by the ringing device toconnect the line and trunk circuits through the condensers to establisha talking circuit.

20. In a telephone exchange system, a line circuit, a repeater circuit,a trunk circuit terminating in an automatic switch, means for operatingthe repeater circuit comprising a calling device and ringing device,condensers, a difl'erentially wound relay bridged across the linecircuit, not responsive to closures of the line circuit, but responsiveto agrounding of said circuit, whereby one side of the trunk circuit isgrounded, and a relay adapted to be energized by the ringing a gerdevice through the intermediation of the difierentially Wound relay toconnect the line and trunk circuits through the condensers to establisha talking circuit.

21. In a telephone exchange system, the combination of line and repeatercircuits, a trunk circuit leading to an automatic switch, and a repeatercircuit including means responsive to initial closure of a line circuitto momentarily ground one member of the trunk circuit and responsive toa prolonged interruption of the line circuit to momentarily ground bothmembers of the trunk circuit.

In testimony whereof I afiix my signature in presence of two witnesses.

GERALD DEAKIN.

Witnesses:

PAULINE J. GLAUCH, E. A. MCCANN.

